NMR measurements and ab initio calculations were applied to determine the barriers to rotation around formally single bonds of the title methyl-beta -ethoxyvinyl ketone, i.e., the vinylogue of the ethyl ester of acetic acid. For comparison, ab initio calculations were performed for alpha,beta -unsaturated, beta -N, and beta -S substituted ketones. The relative height of the rotational barriers for C-sp2-C-sp2 and C-sp2-X bonds of the MeC(O)-CH=CH-Xalkyl(s) analogues was found to be reverse for X = N(alkyl)(2) vs X = O-alkyl or X = S-alkyl. This finding is discussed in terms of differences in the electron density distribution in these molecules, resulting from differences in electron-donating properties of the heteroatoms N, O, and S.